Electrical compensator



A. A. TIRRILL.

ELECTRICAL COMPENSATOR. APPLICATION FILED MAY 28, 1919.

1,344,743. Patented June 29, 1920.

WITNESSES: INVENTOR Al/m A. 77rr/'/ A1YTORNEY UNITED STATES PATENT OFFICE.

ALLEN A. TIRRILL, F PITTSBURGH, PENNSYLVANIA.

ELECTRICAL COMPENSATOR.

Specification of Letters Patent.

Patented June 29, 1920.

Application filed May 28, 1919. Serial No. 300,382.

' and State of Pennsylvania,'have invented a new and useful Improvement in Electrical Compensators, of which the following is a specification, this application being a continuation in part of application Serial No. 114,159, filed August 10, 1916.

My invention relates to compensators whereby voltage regulators and other devices may be caused to respond, in their operation, to the voltage obtaining at a distant point in an electrical distributing circuit.

When it is desired to have a potential regulator for an electrical generator operate to maintain the voltage at a distant point of the connected circuit substantially uniform it is customary to employ a compensator which renders the regulator responsive, in

operation, to the voltage obtaining at the distant point. The compensator usually comprises a resistance element' and an inductance element that receive current through a current-transformer. The current is proportional to that traversing the circuit, and the value of the resistance and the inductance element is adjusted to be approximately in the same ratio as the resistanceand inductance of the line. The connections are so arranged that the counter-electromotive forces set up in the resist-' ance and inductance elements serve to reduce the voltage applied to the regulator winding or windings by an amount propor-,

tional to the drop in voltage in the line to the distant point.-

When the transmission line is of high potential, it is usual to provide both lowpotential and high-potential bus-bars in the generating station and to. employ one or more banks of voltage-changing transformers between them. In'such stations, it obviously is desirable to place the current transformer, that supplies the resistance and inductance elements of the compensator, on the high-potential side of-the voltage-changing transformers where it will be traversed b the total current supplied to the line.

owever, this is often subject to disadvantages, and it is the object of the present invention to provide compensating means that may be employed in connection 1 with the low-tension side of the transformers that The single figure of the accompanying drawing is a diagrammatic view of a system embodying my invention.

Referring to the drawing, a set of hightension bus-bars 1 and 2 are selectively connected to distributing or transmission lines 3, 4 and 5 by means of switches 6, 7 and 8. The high-tension bus-bars 1 and 2 are connected to low-tension bus-bars 9 and 10 by means of potentialtransformers 11, 12 and 13. A plurality of switches 14 and15 are provided for selectively connecting the transformers 11, 12 and. 13 in circuit between the high-tension-bus-bars 1 and 2 and the low-tension bus-bars 9 and 10.

The low-tension bus-bars 9 and 10 receive current from one or ,more generators 16, comprising armatures 17 and field-magnet windings 18. The field windings 18 of the generators 16 are connected, through variable resistors 19, across an exciting circuit comprising conductors 20 and 21. An exciter 22, having an armature 23 and a field winding 24, supplies current to the exciting 1 ing winding 27 that receives current from the exciter generator 22 or from any other suitable source and' is periodically shortcircuited by the engagement and disengagement of a pair of stationary and movable contact terminals 28 and 29, which constitute parts of the main control elements of a vibrating contact regulator. The regulator-further comprises a bell-crank lever 30 having a stationary fulcrum at 31 and a fulcrum at 32 for another lever 33 that is provided with an upwardly and laterally extending arm 34 on which the movable contact terminal 29 is mounted. The lever 30 is actuated b a winding .35 w ich receives current from the low-tension bus-bars 9 and 10 through a transformer 36. A resistor 37, which is inserted in; circuit with the .winding 35, is

an electromagnet having periodically short-circuited by a relay 38 having an energizing winding 39-which is connected in parallel with the winding 27 of the relay 25. The engagement and disencurrent from the low-tension bus-bars 9 and i 10 through the transformer 36 and also through an ohmic-resistance element 41 and an inductive-resistance element 42. The ohmic resistance element 41 and the inductive-resistance element 42 constitute parts of the compensating means whereby the voltage of the secondary winding of the transformer 36 may be compensated or reduced in proportion to the drop in voltage in the lines 2, 3 and 4 and in the transformers 5, 6 and 7 The compensating means further comprises current transformers 42 and 43 associated with the set of connections between the low-tension bus-bars 9 and 10 and the several voltage-changing transformers 11, 12 and 13. Instead of employing two entirely separate and distinct transformers in association with each set of connections it will, of course, be understood that a single transformer having two secondary windings may be employed, if desired. The secondary windings of the transformers 42 are connected in parallel-circuit relation with each other and to a primary winding 44 of a totalizing transformer 45. The secondary winding 44 is provided with a switch arm 46 which is adjusted, in accordance with the number of feeder lines in circuit, to vary the active portion of the secondary winding 44. When all the lines are in service, the switch arm should occupy the position shown in full lines and, when only one line is in circuit, the switch arm should occupy the position shown in dotted lines. The movementsof the arm 46 may be effected manually or they may be effected by any suitable means at present available and not constituting a part of the present invention.

The secondary windings of the current transformers 43 are connected in series with each other and to another primary winding 47 of the totalizing transformer 45. The totalizing transformer is provided with a secondary winding 48 which is connected to the ohmic and the inductance-resistance elements 41 and 42 in such manner that the values of the said elements bear approximately the same relation to each other as the combined ohmic and inductive resistances of the lines 3, 4 and 5 and the transformers 11, 12 and 13. A plurality of switches 49 are provided for shunting the secondary windings of the transformers 43 whenever the voltage transformers associated therewith are-disconnected from the bus-bars. In case one of the transformers 11, 12 or 13 were diconnected from the bus-bars, the secondary winding of the transformer 43, which is associated with the voltage transformer that is disconnected from circuit, would offer a great impedance to the flow of current from the remaining transformers 43 and interfere with the operation of the regulator unless short-circuited. It is unnecessary to provide any such shortcircuiting switches for the secondary windings of the transformers 42, inasmuch as the secondary windings are connected in parallel-circuit relation, and a maximum impedance is desirable in the secondary winding of the transformer 42 which is asso- -ciated with a disconnected. voltage transformer.

v The regulator performs its usual function of controlling the effective value of the resistance of the exciter circuit so as to regulate the voltages of the exciter and of the main generators in accordance with the voltage impressed upon the winding 40. Since the regulator per 86 forms no part of the present invention, it is unnecessary to describe its operation in detail.

The compensator serves to vary the voltage applied to the winding 40 in accordance with the load upon the system and the drop in voltage in the transformers 11, 12 and 13 and in the lines 3, 4 and 5. Since this drop in voltage varies with the number of voltage-changing transformers employed in the circuit between the low and the high-tension bus-bars, it is necessary that the compensator should take care of the number of transformers in use. By properly adjusting the ratios of transformation of the current transformers 42 and 43, this may be readily accomplished. In order to effect this result. the current transformers 42 are so designed as to supply a current of such value to the primary winding 44 of the totalizing transformer 45 as to compensate for the drop in voltage in the lines 3, 4 and 5. It being assumed that the number of lines remains constant, it is only necessary that the current transformers 42 should take account of the total current supplied to the lines and, for that reason, the secondary windings of the transformers are connected in parallel-circuit relation with each other. In case the number of feeder lines is varied, it would be necessary only to vary the active portion of the transformer winding 44 in accordance with the number of feeder lines in service in the manner disclosed in my companion application Serial No. 113,890, filed August 9, 1916. However, since the number of transformers in use may be varied, the amount of current supplied to the primary winding 47 of the totalizing transformer should vary with the number of-voltagechanging transformers in use and, for that reason, the secondary windings of the transformers 43 are connected in series-circuit relation with each other. In the case of the series-connected transformers 43, if only one voltage-changing transformer 'is'in use, the current supplied to the primary winding 47 is proportional to the total amount of cur-- rent delivered from the low-tension bus-bars to the high-tension bus-bars. If twoof the voltage-changing transformers are in use,

the current supplied to the primary winding bars. In this manner, the total current traversi-ng the secondary circuit of the totalizing transformer 45 is caused to be dependent upon the number of voltage-changing transformers in use between the low and the hightension'bus-bars, and, as before stated, by properly selecting the transformation ratios of the current transformers 42 and 43, substantially correct compensation may be effected, irrespective of the number of voltage-changing transformers in use. The invention may, of course, be employed with any desired number of voltage-changing transformers.

Modifications in the system and arrangement and location of parts may be made within the -spirit and scope of my invention, and such modificationsare intended to be covered by the, appended claims.

I claim as my invention:

1. In an electrical system, the combination with -a plurality of voltage-changing transformers, a plurality of feeder circuits, and selective switching means associated with the transformers, of current-transforming means associated, respectively, with the connections to the voltage-changing transformers and comprising two sets of secondary windings, those of one set being connected in parallel and those of the other set being connected in series, totalizing transforming means having two primary windings associated, respectively, with the said setsof secondary wmdmgs, resistance and inductance devices to which the totalizingtransforming means supplies current, and an inselective switching means associated with the transformers, of current-transforming means associated, respectively, with the connections to the voltage-changing transformers and comprising two sets of secondary windings, those of one set being connected in parallel and those of the other set being connected in series, resistance and inductance elements to which the said secondary windings deliver current, and an instrument having a winding the circuit of which includes the'said resistance and inductance elements.

3. In an electrical system, the combination with a plurality of-voltage-changing transformers, a plurality of feeder circuits, and selective switching means associated with the transformers, of current-transforming means associated, respectively, with the connections to the voltage-changing transformers and comprising two sets of secondary windings, those of one set being connected in parallel and those of the other set being connected in series, an instrument having a winding, and counter-electromotive-force means in circuit with the instrument winding and supplied with current from said secondary windings.

4. In an electrical system, the combination with a supply circuit, a plurality of voltage transformers and a plurality of feeder circuits-connected through the voltage transformers to the supply circuit, of a plurality of series-connected current transformers associated with said voltage transformers, and means controlled by said current transformers for automatically regulating the supply-circuit voltage in accordance with the number of voltage transformers in circuit.

5. In an electrical system, the combination with a supply circuit, a plurality of voltage transformers, and a plurality of feeder circuits connected, through, said transformers, to the supply circuit, of a plurality of series-connected current transformers associated with said voltage transformers, a plurality of parallel-connected current, transformers associated with said feeder circuits, and means associated with said current transformers for regulating the supply-circuit voltage in accordance with the number of voltage transformers in circuit and in accordance with feeder-circuit conditions. v

6. In an electrical system, the combination with a supply circuit, a plurality of feeder circuits, a plurality of voltage transformers, and means comprising'a plurality of switches for connecting the feeder circuits through the transformers to the supply circuit, of means associated with said connecting means and comprising a plurality of current transformers connected in seriescircuit relation, and means associated with said current-transforming means for regulating the supply-circuit voltage in accordance with the number of voltage transformers connected in circuit.

7. In an electrical system, the combination with a supply circuit, a plurality of feeder circuits, a plurality of voltage transformers, and means comprising switches for connecting the feeder circuits through the transformers to the supply circuit, of means associated with said connecting means and comprising a plurality of current transformers connected in parallel-circuit relation and a plurality of current transformers connected in series-circuit relation, means associated with said current-transforming means for regulating the supplycircuit voltage in accordance With the numand I ber of feeder circuits connected to the supply circuit and in accordance With the number of voltage transformers in circuit.

8. In an electrical system, the combination with a supply circuit, a plurality of voltage transformers and a feeder circuit connected through voltage transformers to the supply circuit, of a plurality of seriesconnected current transformers associated with said voltage transformers and means controlled by said current transformers for automatically regulating the supply-circuit voltage in accordance with the number of voltage transformers in circuit.

In testimony whereof I have hereunto subscribed my name this 26th day of May, 1919.

ALLEN A. TIRRILL. 

